Photographic lens system

ABSTRACT

A photographic lens system having a field angle of 70° or wider and designed for use with compact cameras having a relative aperture of F/3.5 comprising a first positive meniscus lens component having a convex surface on the object side, a second positive meniscus lens component having a convex surface on the object side, a third negative meniscus lens component having a convex surface on the object side, a fourth lens component having positive refractive power, and a fifth lens component comprising a negative lens element and having positive refractive power as a whole.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a photographic lens system having afield angle of 70° to wider and designed for use with a compact camera(adopting for a photographic lens and a view finder which are designedas separate units) having a relative aperture of F/3.5.

(b) Description of the Prior Art

As lens systems for use with a compact camera, there have conventionallybeen known triplet type, Tessar type and variant types thereof. However,these conventional photographic lens systems had field angles on theorder of 60° at maximum. Recently, there are known the so-calledtelephoto type of lens systems having short total lengths for compactcameras comprising a positive front lens group and a negative rear lensgroup. These lens systems are also designed for field angles on theorder of 60° to 65°.

Generally, it is important to favorably correct curvature of field forobtaining a lens system having a large field angle. In order to correctcurvature of field, it is necessary to minimize Petzval sum, and forthis purpose in turn, it is necessary to arrange a negative lenscomponent in the lens system. As this nagative lens component has alower refractive index, Petzval sum is smaller and curvature of field iscorreted more favorably. In a lens system for use with compact cameras,positive lens components are arranged on the front side of the lenssystem for shortening the distance as measured from the first lenssurface to the film surface (hereinafter referred to as "total length oflens system"). In order to obtain a shorter total length of lens system,these positive lens components must have higher refractive power, whichallows negative spherical aberration to be aggravated. Therefore, it isgeneral to arrange a negative lens component between these positive lenscomponents so as to correct curvature of field by minimizing Petzval sumand, at the same time, correct the negative spherical aberration. Thefunction to correct this negative spherical aberration is more effectivewhen the object side surface of the negative lens component is concavetoward object to be photographed and has smaller radius of curvaturesince the paraxial ray incident on this surface has large angle ofincidence at higher level on the surface. Therefore, a lower refractiveindex of this negative lens component is more advantageous forcorrecting curvature of field and spherical aberration. When thissurface has a small radius of curvature, however, it produces coma sinceangle of incidence is largely different between the upper and lower raysof the offaxial ray incident on this surface at large field angle.Therefore, coma is aggravated abruptly at larger field angle. For thisreason, it has hitherto been difficult to design a lens system having afield angle of 70° or larger for use with compact cameras.

As a conventional example having a lens composition similar to that ofthe lens system according to the present invention, there has alreadyknown the one disclosed by Japanese Unexamined Published PatentApplication No. 95207/81. This lens system is designed compact but has afield angle on the order of 60° to 65°.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a photographiclens system having a field angle of 70° or wider and designed for usewith compact cameras wherein production of coma is prevented by using anegative meniscus lens component having a convex surface on the objectside as a third lens component, the negative spherical aberrationcorrecting function weakened by said third lens component issupplemented by arranging a first and second positive meniscus lenscomponents each having a convex surface on the object side, wherebyproduction of spherical aberration is minimized.

The photographic lens system according to the present inventioncomprises a first positive meniscus lens component having a convexsurface on the object side, a second positive meniscus lens componenthaving a convex surface on the object side, a third negative meniscuslens component having a convex surface on the object side, a fourth lenscomponent having positive refractive power, and a fifth lens componentcomprising a negative lens element and having positive refractive poweras a whole. Further, the lens system according to the present inventionis so designed as to satisfy the conditions mentioned below:

    1.5/f<1/r.sub.1 <3.0/f                                     (1)

    0<1/r.sub.5 <1.2/f                                         (2)

wherein the reference symbols are defined as follows:

r₁ : radius of curvature on the object side surface of said first lenscomponent

r₅ : radius of curvature on the object side surface of said third lenscomponent

f: focal length of the lens system as a whole

The condition (1) defines curvature on the object side surface of saidfirst lens component. When this surface has a large curvature, theparaxial ray has a larger angle of incidence at higher level on thesurface and subjected to stronger refraction when the lens system isfocused on an object located at a short distance. The negative sphericalaberration is aggravated accordingly. In other words, a curvature on theobject side surface of the first lens component exceeding the upperlimit of the condition (1) allows spherical aberration to have a largenegative value when the lens system is focused on an object located at ashort distance. If the lower limit of the condition (1) is exceeded, incontrast, the first lens component has weaker refractive power, and thesecond lens component must have stronger power for making up for theweakened power of the first lens component. Accordingly, the second lenscomponent produces negative spherical aberration at a too large a degreeto be corrected.

The condition (2) defines curvature on the object side surface of saidthird lens component. If 1/r₅ is smaller than the lower limit of thecondition (2), coma will be aggravated. if the upper limit of thecondition (2) is exceeded, in contrast, it will be impossible to correctspherical aberration.

The lens system having the above-described lens constraction andsatisfying the conditions (1) and (2) can accomplish the object of thepresent invention. However, a more favorable lens system can be obtainedby designing it as described below:

In order to design the first and second lens components so as to produceless spherical aberraiton, it is desirable to select refractive index n₁of the first lens component and refractive index n₂ of the second lenscomponent so as to satisfy the following condition (3):

    1.7<(n.sub.1 +n.sub.2)/2                                   (3)

If this condition (3) is not satisfied, the first and second lenscomponents will produce negative spherical aberration at anuncorrectable degree.

It is desirable to design the fifth lens component as a lens componentcomprising a negative lens element arranged on the extreme image sideand having weakly positive refractive power as a whole. By arranging anegative lens element on the extreme image side as described above, itis possible to make the lens system have the lens constraction similarto that of so-called telephoto type, shorten total length of the lenssystem and minimize diameter of the rear lens component. However, thisnegative lens element produces positive distortion. Therefore, it isadvantageous for preventing production of distortion to design thisnegative lens element as a meniscus element having a convex surface onthe image side. Further, focal length f₅ n of this negative lens elementshould desirably satisfy the following condition (4):

    0.5<|f.sub.5 n|/f<7.0, f.sub.5 n<0       (4)

If f₅ n is smaller than the lower limit of the condition (4), positivedistortion will be aggravated. If f₅ n exceeds the upper limit of thecondition (4), in contrast, total length of the lens system will beprolonged and diameter of the rear lens component will be enlarged,making the lens system unsuited for use with compact cameras.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view illustrating lens composition ofembodiments 1, 2 and 4 of the photographic lens system according to thepresent invention;

FIG. 2 shows a sectional view illustrating lens composition of anembodiment 3 of the lens system according to the present invention; and

FIG. 3 through FIG. 6 show curves illustrating aberrationcharacteristics of the Embodiments 1 through 4 respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, numerical data will be described as preferred embodiments of thephotographic lens system according to the present invention:

    ______________________________________                                        Embodiment 1                                                                  r.sub.1 = 46.5365                                                                        d.sub.1 = 5.8088                                                                         n.sub.1 = 1.81600                                                                        ν.sub.1 = 46.62                           r.sub.2 = 53.2225                                                                        d.sub.2 = 0.3335                                                   r.sub.3 = 31.3160                                                                        d.sub.3 = 8.3383                                                                         n.sub.2 = 1.81600                                                                        ν.sub.2 = 46.62                           r.sub.4 = 50.8091                                                                        d.sub.4 = 4.3359                                                   r.sub.5 = 182.3270                                                                       d.sub.5 = 2.9044                                                                         n.sub.3 = 1.76182                                                                        ν.sub.3 = 26.55                           r.sub.6 = 25.7941                                                                        d.sub.6 = 2.5559                                                   r.sub.7 = 39.6304                                                                        d.sub.7 = 7.8127                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 46.03                           r.sub.8 = -80.2598                                                                       d.sub.8 = 2.9174                                                                         n.sub.5 = 1.51633                                                                        ν.sub.5 = 64.15                           r.sub.9 = 118.9013                                                                       d.sub.9 = 2.3235                                                   r.sub.10 = ∞  (stop)                                                               d.sub.10 = 10.8922                                                 r.sub.11 = 447.5011                                                                      d.sub.11 = 8.3328                                                                        n.sub.6 = 1.77250                                                                        ν.sub.6 = 49.66                           r.sub.12 = -212.8122                                                                     d.sub.12 = 3.9982                                                  r.sub.13 = -65.0478                                                                      d.sub.13 = 6.6671                                                                        n.sub.7 = 1.59270                                                                        ν.sub.7 = 35.29                           r.sub.14 = -87.3047                                                                      f = 100,   F/3.5,     |f.sub.5n |/f = 4.845      Embodiment 2                                                                  r.sub.1 = 52.1997                                                                        d.sub.1 = 5.8063                                                                         n.sub.1 = 1.81600                                                                        ν.sub.1 = 46.62                           r.sub.2 = 59.0464                                                                        d.sub.2 = 0.3334                                                   r.sub.3 = 29.9107                                                                        d.sub.3 = 7.3346                                                                         n.sub.2 = 1.81600                                                                        ν.sub.2 = 46.62                           r.sub.4 = 45.7540                                                                        d.sub.4 = 5.3342                                                   r.sub.5 = 131.7944                                                                       d.sub.5 = 2.9031                                                                         n.sub.3 = 1.76182                                                                        ν.sub.3 = 26.55                           r.sub.6 = 23.8092                                                                        d.sub.6 = 2.5548                                                   r.sub.7 = 33.5841                                                                        d.sub.7 = 7.8093                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 43.70                           r.sub.8 = -84.0763                                                                       d.sub.8 = 2.9162                                                                         n.sub.5 = 1.51633                                                                        ν.sub.5 = 64.15                           r.sub.9 = 79.8070                                                                        d.sub.9 = 2.3225                                                   r.sub.10 = ∞ (stop)                                                                d.sub.10 = 14.1832                                                 r.sub.11 = 609.6062                                                                      d.sub.11 = 8.3347                                                                        n.sub.6 = 1.77250                                                                        ν.sub.6 = 49.66                           r.sub.12 = -139.9410                                                                     d.sub.12 = 5.5168                                                  r.sub.13 = -133.1382                                                                     d.sub.13 = 6.6678                                                                        n.sub.7 = 1.59270                                                                        ν.sub.7 = 35.29                           r.sub.14 = -354.2207                                                                     f = 100,   F/3.5,     |f.sub.5n |/f = 3.640      Embodiment 3                                                                  r.sub.1 = 41.9452                                                                        d.sub.1 =  7.3333                                                                        n.sub.1 = 1.88300                                                                        ν.sub.1 = 40.76                           r.sub.2 = 48.7535                                                                        d.sub.2 = 0.3333                                                   r.sub.3 = 35.9194                                                                        d.sub.3 = 7.0000                                                                         n.sub.2 = 1.88300                                                                        ν.sub.2 = 40.76                           r.sub.4 = 57.7933                                                                        d.sub.4 = 4.6667                                                   r.sub.5 = 596.2729                                                                       d.sub.5 = 2.9026                                                                         n.sub.3 = 1.84666                                                                        ν.sub.3 = 23.88                           r.sub.6 = 32.2834                                                                        d.sub.6 = 2.5543                                                   r.sub.7 = 51.1059                                                                        d.sub.7 = 9.9157                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 41.98                           r.sub.8 = -284.3712                                                                      d.sub.8 = 1.4667                                                   r.sub.9 = ∞ (stop)                                                                 d.sub.9 = 10.9788                                                  r.sub.10 = 623.4936                                                                      d.sub.10 = 15.6985                                                                       n.sub.5 = 1.80610                                                                        ν.sub.5 = 40.95                           r.sub.11 = -87.3058                                                                      d.sub.11 =  5.3328                                                 r.sub.12 = -50.1661                                                                      d.sub.12 = 4.6822                                                                        n.sub.6 = 1.58267                                                                        ν.sub.6 = 46.33                           r.sub.13 = -250.0457                                                                     f = 100,   F/3.5,     |f.sub.5n |/f = 1.086      Embodiment 4                                                                  r.sub.1 = 53.0930                                                                        d.sub.1 = 5.8053                                                                         n.sub.1 = 1.81600                                                                        ν.sub.1 = 46.62                           r.sub.2 = 59.9196                                                                        d.sub.2 = 0.3333                                                   r.sub.3 = 29.5248                                                                        d.sub.3 = 8.3333                                                                         n.sub.2 = 1.81600                                                                        ν.sub.2 = 46.62                           r.sub.4 = 49.9079                                                                        d.sub.4 = 4.3333                                                   r.sub.5 = 139.2884                                                                       d.sub.5 = 2.9026                                                                         n.sub.3 = 1.76182                                                                        ν.sub.3 = 26.55                           r.sub.6 = 23.8537                                                                        d.sub.6 = 2.5543                                                   r.sub.7 = 37.4819                                                                        d.sub.7 = 7.8080                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 43.70                           r.sub.8 =  -80.2117                                                                      d.sub.8 = 2.9157                                                                         n.sub.5 = 1.51633                                                                        ν.sub.5 = 64.15                           r.sub.9 = 97.2536                                                                        d.sub.9 = 2.3221                                                   r.sub.10 = ∞ (stop)                                                                d.sub.10 = 13.9245                                                 r.sub.11 = 327.4500                                                                      d.sub.11 = 8.7942                                                                        n.sub.6 = 1.77250                                                                        ν.sub.6 = 49.66                           r.sub.12 = -293.7912                                                                     d.sub.12 = 5.8477                                                  r.sub.13 = -66.4262                                                                      d.sub.13 = 7.3688                                                                        n.sub.7 = 1.59270                                                                        ν.sub.7 = 35.29                           r.sub.14 = -87.7115                                                                      f = 100,   F/3.5,     |f.sub.5n |/f =            ______________________________________                                                                         5.301                                    

wherein the reference symbols r₁, r₂, . . . represent radii of curvatureon the surfaces of the respective lens elements, the reference symbolsd₁, d₂, . . . designate thicknesses of the respective lens elements andairspaces reserved therebetween, the reference symbols n₁, n₂, . . .denote refractive indices of the respective lens elements and thereference symbols ν₁, ν₂, . . . represent Abbe's numbers of therespective lens elements.

In all the embodiments described above, the fifth lens componentcomprises a positive element and a negative element. The Embodiments 1,2 and 4 have the lens composition illustrated in FIG. 1 in which thefourth lens component is a cemented doublet. The Embodiment 3 has thelens composition shown in FIG. 2 in which the fourth lens componentconsists of a single element.

I claim:
 1. A photographic lens system comprising a first positivemeniscus lens component having a convex surface on the object side, asecond positive meniscus lens component having a convex surface on theobject side, a third negative meniscus lens component having a convexsurface on the object side, a fourth lens component having positiverefractive power, and a fifth lens component comprising a negative lenselement and having positive refractive power as a whole, said negativelens element in said fifth lens component being arranged on the extremeimage side and being a negative meniscus lens, and said lens systembeing so designed as to satisfy the following conditions (1), (2), (3)and (4):

    1.5/f<1/r.sub.1 <3.0/f                                     (1)

    0<1/r.sub.5 <1.2/f                                         (2)

    1.7<(n.sub.1 +n.sub.2)/2                                   (3)

    0.5<|f.sub.5 n|/f<7.0, f.sub.5 n<0       (4)

wherein the reference symbol f represents focal length of the lenssystem as a whole, the reference symbol r₁ designates radius ofcurvature on the object side surface of said first lens component, thereference symbol r₅ denotes radius of curvature on the object sidesurface of said third lens component, the reference symbols n₁ and n₂represent refractive indices of said first and second lens componentsrespectively, and the reference symbol f₅ n designates focal length ofthe negative element comprised in said fifth lens component.
 2. Aphotographic lens system according to claim 1 wherein said forth lenscomponent is a positive cemented doublet, and said fifth lens componentconsists of a positive element and a negative element.
 3. A photographiclens system according to claim 1 wherein said fourth lens componentconsists of a single positive element, and said fifth lens componentconsists of a positive element and a negative element.
 4. A photographiclens system according to claim 2 having the following numerical data:

    ______________________________________                                        r.sub.1 = 46.5365                                                                        d.sub.1 = 5.8088                                                                         n.sub.1 = 1.81600                                                                        ν.sub.1 = 46.62                           r.sub.2 = 53.2225                                                                        d.sub.2 = 0.3335                                                   r.sub.3 = 31.3160                                                                        d.sub.3 = 8.3383                                                                         n.sub.2 = 1.81600                                                                        ν.sub.2 = 46.62                           r.sub.4 = 50.8091                                                                        d.sub.4 = 4.3359                                                   r.sub.5 = 182.3270                                                                       d.sub.5 = 2.9044                                                                         n.sub.3 = 1.76182                                                                        ν.sub.3 = 26.55                           r.sub.6 = 25.7941                                                                        d.sub.6 = 2.5559                                                   r.sub.7 = 39.6304                                                                        d.sub.7 = 7.8127                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 46.03                           r.sub.8 = -80.2598                                                                       d.sub.8 = 2.9174                                                                         n.sub.5 = 1.51633                                                                        ν.sub.5 = 64.15                           r.sub.9 = 118.9013                                                                       d.sub.9 = 2.3235                                                   r.sub.10 = ∞ (stop)                                                                d.sub.10 = 10.8922                                                 r.sub.11 = 447.5011                                                                      d.sub.11 = 8.3328                                                                        n.sub.6 = 1.77250                                                                        ν.sub.6 = 49.66                           r.sub.12 = -212.8122                                                                     d.sub.12 = 3.9982                                                  r.sub.13 = -65.0478                                                                      d.sub.13 = 6.6671                                                                        n.sub.7 = 1.59270                                                                        ν.sub.7 = 35.29                           r.sub.14 = -87.3047                                                                      f = 100,   F/3.5,     |f.sub.5n |/f =            ______________________________________                                                                         4.845                                    

wherein the reference symbols r₁, r₂, . . . represent radii of curvautreon the surfaces of the respective lens elements, the reference symbolsd₁, d₂, . . . designate thicknesses of the respective lens elements andairspaces reserved therebetween, the reference symbols n₁, n₂, . . .denote refractive indices of the respective lens elements and thereference symbols ν₁, ν₂, . . . represent Abbe's numbers of therespective lens elements.
 5. A photographic lens system according toclaim 2 having the following numerical data:

    ______________________________________                                        r.sub.1 = 52.1997                                                                        d.sub.1 = 5.8063                                                                         n.sub.1 = 1.81600                                                                        ν.sub.1 = 46.62                           r.sub.2 = 59.0464                                                                        d.sub.2 = 0.3334                                                   r.sub.3 = 29.9107                                                                        d.sub.3 = 7.3346                                                                         n.sub.2 = 1.81600                                                                        ν.sub.2 = 46.62                           r.sub.4 = 45.7540                                                                        d.sub.4 = 5.3342                                                   r.sub.5 = 131.7944                                                                       d.sub.5 = 2.9031                                                                         n.sub.3 = 1.76182                                                                        ν.sub.3 = 26.55                           r.sub.6 = 23.8092                                                                        d.sub.6 = 2.5548                                                   r.sub.7 = 33.5841                                                                        d.sub.7 = 7.8093                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 =43.70                            r.sub.8 = -84.0763                                                                       d.sub.8 = 2.9162                                                                         n.sub.5 = 1.51633                                                                        ν.sub.5 = 64.15                           r.sub.9 = 79.8070                                                                        d.sub.9 = 2.3225                                                   r.sub.10 = ∞ (stop)                                                                d.sub. 10 = 14.1832                                                r.sub.11 = 609.6062                                                                      d.sub.11 = 8.3347                                                                        n.sub.6 = 1.77250                                                                        ν.sub.6 = 49.66                           r.sub.12 = -139.9410                                                                     d.sub.12 = 5.5168                                                  r.sub.13 = -133.1382                                                                     d.sub.13 = 6.6678                                                                        n.sub.7 = 1.59270                                                                        ν.sub.7 = 35.29                           r.sub.14 = -354.2207                                                                     f = 100,   F/3.5,     |f.sub.5n |/f =            ______________________________________                                                                         3.640                                    

wherein the reference symbols r₁, r₂, . . . represent radii of curvatureon the surfaces of the respective lens elements, the reference symbolsd₁, d₂, . . . designate thicknesses of the respective lens elements andairspaces reserved therebetween, the reference symbols n₁, n₂, . . .denote refractive indices of the respective lens elements and thereference symbols ν₁, ν₂, . . . represent Abbe's numbers of therespecitve lens elements.
 6. A photographic lens system according toclaim 3 having the following numerical data:

    ______________________________________                                        r.sub.1 = 41.9452                                                                        d.sub.1 = 7.3333                                                                         n.sub.1 = 1.88300                                                                        ν.sub.1 = 40.76                           r.sub.2 = 48.7535                                                                        d.sub.2 = 0.3333                                                   r.sub.3 = 35.9194                                                                        d.sub.3 = 7.0000                                                                         n.sub.2 = 1.88300                                                                        ν.sub.2 = 40.76                           r.sub.4 = 57.7933                                                                        d.sub.4 = 4.6667                                                   r.sub.5 = 596.2729                                                                       d.sub.5 = 2.9026                                                                         n.sub.3 = 1.84666                                                                        ν.sub.3 = 23.88                           r.sub.6 = 32.2834                                                                        d.sub.6 = 2.5543                                                   r.sub.7 = 51.1059                                                                        d.sub.7 = 9.9157                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 41.98                           r.sub.8 = -284.3712                                                                      d.sub.8 = 1.4667                                                   r.sub.9 = ∞ (stop)                                                                 d.sub.9 = 10.9788                                                  r.sub.10 = 623.4936                                                                      d.sub.10 = 15.6985                                                                       n.sub.5 = 1.80610                                                                        ν.sub.5 = 40.95                           r.sub.11 = -87.3058                                                                      d.sub.11 = 5.3328                                                  r.sub.12 = -50.1661                                                                      d.sub.12 = 4.6822                                                                        n.sub.6 = 1.58267                                                                        ν.sub.6 = 46.33                           r.sub.13 = -250.0457                                                                     f = 100,   F/3.5,     |f.sub.5n |/f =            ______________________________________                                                                         1.086                                    

wherein the reference symbols r₁, r₂, . . . represent radii of curvatureon the surfaces of the respective lens elements, the reference symbolsd₁, d₂, . . . designate thicknesses of the respective lens elements andairspaces reserved therebetween, the reference symobls n₁, n₂, . . .denote refracitve indices of the respective lens elements and thereference symbols ν₁, ν₂, . . . represent Abbe's numbers of therespective lens elements.
 7. A photographic lens system according toclaim 2 having the following numerical data:

    ______________________________________                                        r.sub.1 = 53.0930                                                                        d.sub.1 = 5.8053                                                                         n.sub.1 = 1.81600                                                                        ν.sub.1 = 46.62                           r.sub.2 = 59.9196                                                                        d.sub.2 = 0.3333                                                   r.sub.3 = 29.5248                                                                        d.sub.3 = 8.3333                                                                         n.sub.2 = 1.81600                                                                        ν.sub.2 = 46.62                           r.sub.4 = 49.9079                                                                        d.sub.4 = 4.3333                                                   r.sub.5 = 139.2884                                                                       d.sub.5 = 2.9026                                                                         n.sub.3 = 1.76182                                                                        ν.sub.3 = 26.55                           r.sub.6 = 23.8537                                                                        d.sub.6 = 2.5543                                                   r.sub.7 = 37.4819                                                                        d.sub.7 = 7.8080                                                                         n.sub.4 = 1.72000                                                                        ν.sub.4 = 43.70                           r.sub.8 = -80.2117                                                                       d.sub.8 = 2.9157                                                                         n.sub.5 = 1.51633                                                                        ν.sub.5 = 64.15                           r.sub.9 = 97.2536                                                                        d.sub.9 = 2.3221                                                   r.sub.10 = ∞ (stop)                                                                d.sub.10 = 13.9245                                                 r.sub.11 = 237.4500                                                                      d.sub.11 = 8.7942                                                                        n.sub.6 = 1.77250                                                                        ν.sub.6 = 40.66                           r.sub.12 = -293.7912                                                                     d.sub.12 = 5.8477                                                  r.sub.13 = -66.4262                                                                      d.sub.13 = 7.3688                                                                        n.sub.7 = 1.59270                                                                        ν.sub.7 = 35.29                           r.sub.14 = -87.7115                                                                      f = 100,   F/3.5,     |f.sub.5n |/f =            ______________________________________                                                                         5.301                                    

wherein the reference symbols r₁, r₂, . . . represent radii of curvatureon the surfaces of the respective lens elements, the reference symbolsd₁, d₂, . . . designate thicknesses of the respective lens elements andairspaces reserved therebetween, the referece symbols n₁, n₂, . . .denote refracitve indices of the respective lens elements and thereference symbols ν₁, ν₂, . . . represent Abbe's numbers of therespective lens elements.